A Study on the Relationship between Tightening Torque and Axial Force of Bolts at the Tower Top Flange of Wind Turbine

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  • 風車タワートップフランジボルトにおける締付トルクと導入軸力の関係に関する研究
  • カザグルマ タワートップフランジボルト ニ オケル シメツケ トルク ト ドウニュウジクリョク ノ カンケイ ニ カンスル ケンキュウ

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Description

In this study, the relationship between tightening torque and axial force of bolt at the tower top flange was investigated through a laboratory test with flange section models and a 750 kW wind turbine which had experienced the damages of bolt at the tower top flange. Tightening torques and axial forces of bolt in these tests were measured directly by using torque wrenches and strain gauges inserted in the bolts. Existence of lubricant had a great influence on the axial force of bolt, while types of torque wrench had a small impact on those. The expected axial force of bolt was obtained by torque wrenches and the variation was around 10%. A method for quantitatively evaluating decrease in axial force of bolt was proposed by measuring rotation of bolt. The damaged bolts in the wind turbine were also investigated and the axial forces at the damaged bolts were completely lost, while those at the loosed bolts were more than 30% of the initial value. It was found that the axial force of bolt decreased by about 20% after 500 hours from the exchange of bolts. This indicates that retightening is necessary for wind turbine tower bolts.

Journal

  • Wind Energy

    Wind Energy 40 (2), A_13-A_18, 2016

    Japan Wind Energy Association

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